Bar screen scraper



Aug. 30, 1938. R. E. BRIGGS BAR SCREEN SCRAPER Filed Aug. 16, 1934 sSheets-Sheet 1 EQBEQT E. BEKEGS Aug. 30, 1938. R. EJBRIGGS 2,128,346

I BAR SCREEN SCRAPER Filed Aug. 16, 1934 s Sheets-Sheet 2 5y 7 '7) I 4 vI Aug. 30, 1938. R. E. BRIGGS 2,128,346

POBEPT E-BPIGGS,

Patented Aug. so, 1938 2,128,346

UNITED STATES PATENT OFFICE BAR SCREEN SCRAPER Robert E. Briggs,Columbus, Ohio, assignor to The Jeffrey Manufacturing Company, acorporation of Ohio Application August 16, 1934, Serial No. 740,159

14 Claims. (01. 210-176) This invention relates to apparatus for removtobe mounted upon the supporting frame D. Also ing solid refuse or trashfrom a stream of water, can'ied upon said frame D is a driving means Esuch as a sewage'stream, preliminary to the passfor driving of said rakeor scraper C. ing of said water to settling tanks. 'I'he screen A isformed by a pair of spaced One object of the invention is to provide inthe side plates Ill, l which are adapted to be fixed above mentionedclass of apparatus a rake or to the side walls of the concrete tank ortrough scraper which is adapted to operate to clean the II intowhich thescreen A projects, by lugs l0 screen of said apparatus efficiently.which project inwardly thereof and fit into verti- Another and importantobject of the invention cal slots l I extending upwardly from the bottomis to provide for an interleaving of the teeth of of plates III, II].Said lugs may be threaded to 10 a rake or scraper and the screen bars ofa screen receive nuts l3. Between the side plates I0, ID, of the abovementioned type at a position in adand perpendicular thereto, extend thelateral vance of an area on said screen at which refuse spacing andsupporting bars l2 which may be tends to collect or pile up. welded tosaid side plates I0, I!) at their ends Another object of the inventionis to provide and thereby be rigidly attached thereto. Also bein anapparatus of the class above described, a tween said side plates Ill,l0, and parallel thererake for cleaning the screen bars of a screen andwith, extend a plurality of screen bars l3 having spring cam means forurging the rake teeth in spaced downward extensions l2 (Fig. 3) carriedinterleaving relation with said screen bars adupon said lateral bars I2and rigidly attached J'acent the bottom of the screen where refusethereto, as by welding. Each of said screen bars tends to collect, forthe purpose of yieldingly 13 preferably comprises an upstanding platemaintaining said interleaving relation. Spaced apart from the nextspaced screen bar Other objects of the invention will appear herewherebya screen is formed. Said bars l2 not inafter, the novel features andcombinations only give rigidity to the screen bars but also keep In thedrawings: large piece of material between two of them tends Fig. 1 is afront elevational view of the device to spread them apart and move themadj cent embodying my invention, illustrating the assothe next bars.Said bars l2 therefore maintain ciated tank or trough in section; thescreen bars l3 in proper spaced relation to do Fig. 2 is a sideelevational view of the device in provide proper alignment thereofforthe ready 30 Fig. 1, illustrating the several floor levels insecpassage of the teeth of the rake or scraper theretiOn; through andprevent increased friction between Fig. 3 is' an enlarged detail viewshowing the the rake or scraper teeth and said screen bars. constructionof my device adjacent the refuse Adjacent the bottom wall of the tank ortrough 35. collecting or bottom portion thereof and taken II and setwith its upper face in alignment with along the line 3-3 of Fig. 4,looking in the directhe upper face of said lower wall is a plate l4.131011 of the arrows; Said plate is held rigid in the concrete formingFig. 4 is a sectional view taken along the line the bottom-wall of tankor trough II by adhesion 6-4 of Fig. 3, looking in the direction ofthe...of the lower face of said. plate with the adjacent arrows; dconcrete. The screen bars l3 of the screen A, 40

Fig. 5 is an enlarged perspective view of the through which the rawrefuse-containing fluid as lower portion of my invention showing therake received from a sewer is adapted to flow, as indior scraperinterleaved with the extension of the cated by the arrows in Fig. 2, areextended from screen. i an inclined position where they form said screenThe invention here involved relates primarily to a substantiallyhorizontal position above the 45 to an improvement in the materialhandling applate M where they form extensions [5. The paratus disclosedin my co-pending application, said extensions ii are welded adjacenttheir bot- Serial No. 701,548 filed December 8, 1933. tom edges to thetop of said plate l4 whereby Referring'particularly to Figs. 1 and 2 ofthe they are prevented from spreading, thus being drawings, theapparatus comprises a screen A maintained in proper alignment to receivethe 50 adapted to be partially submerged in a tank or teeth of the rakeor scraper C. Said plate also trough into which the liquid, such assewage, is holds the extensions down against any tendency to pass beforeentering a settling tank. The guide thereof to move upwardly. tracks Bare provided with draft chains carrying The side plates ill, H), whichare of greater 5; the rake or scraper C, which tracks B are adapteddepth than the screen bars l3 adjacent the being set forth in theappended claims. them properly spaced when, as for example, a 25- screenportion A, are reduced in depth adjacent said plate M to a depth equalof said screen bars l3. Said side plates l0, ID are also welded adjacenttheir bottom edges to said plate l4. Saidextensions I5 and the sideplates l9, l8 preferably project beyond the end of the plate l4 and aretapered at I6 to meet the bottom wall of the tank or through guide andto guide the refuse from the refuse laden stream on to the screen A.Brackets I5 are provided to extend over the two side screen barextensions and are attached to the side wall of the tank or trough H.brackets I5 prevent any tendency for the extensions |5 to. pull theplate M from its anchorage with the bottom of said tank or trough Theupper portion of said screen A is rigidly attached to the concretesupporting floor ll of said tank or trough by the channel member llwelded to said screen A and buried in said floor l1, and is formed rigidwith the curve plate l8, as by welding. Said plate I8 is carried by theframe D and has a discharge lip IQ for discharging refuse on the floorII, or, if desired, on a conveyor belt or into refuse receptacles or agrinder. If the refuse is discharged on the floor the liquid portion andsmall particlesthereof may return to the sewer stream through drain l8in floor I'I.

The curved guide tracks. B are formed by a pair of spaced angle members20, 20 which are bent upon themselves to form a substantially U- shapedguide track for the continuous rake or scraper carrying draft chains 2|,2|. Said angle members 28, 20 are mounted upon the face plates 22, 22,as by welding. The open side of theguide channels formed by said anglemembers 29, 29 are provided with the welded retainer plates 23, 23 toretain said chains 2|, 2| in their tracks. Said tracks B are mounted andsupported on the frame D and, if desired, may be attached at intervalsto the side walls of the tank or trough I. The continuous chains 2|, 2|are adapted to be driven by sprockets 24, 24 mounted on the shaft 25carried insuitable bearings upon the frame D. Said shaft 25 is adaptedto be driven from the motor 26 by driving means E, through the speedreduction device 21 and the sprocket and chain means 28. A chaintensioning device 29 may be provided for said sprocket and chain device28.

Also carried upon the frame D-is a scraper cleaning mechanism comprisinga transverse bar 38 carried on the arms 3|, 3| pivoted to said frame Dat 32 and weighted by the counterweight 33 on the lever 34 to maintainsaid cross bar 3|! in wiping contact with the rake or scraper C duringthemovement thereof past the discharge lip l9. The frame D may also beprovided with a ladder 35'to provide ready access to the. drivingmechanism E.

The construction of'the rake or scraper C is best illustrated in Figs.3, 4 and 5 andcomprises a central angle member 36 carried between thelaterally-spaced brackets 31, 31 having the arms 38, 38 pivoted to theoppositely-disposed, inwardly-projecting bolts 39, 39 extending throughjournal bearings 40,40 on said arms 38, 38, said bolts 39, 39 beingcarried upon the oppositelydisposed plates 4|, 4|, which plates arecarried by the extended link bolts 42, 42 of the chains 2|, 2|. The linkbolts 42, 42 are each provided with a pair of spaced nuts 43, 43 foradjustably positioning the plates 4|, 4|. provided withinwardly-projecting stop lugs 44, 44 to limit the movement of the arms38, 38 about These Said plates 4|, 4| are their pivot points 39, 39 inone direction of movement and with the lugs 45, 45 to limit the pivotalmovement of said arms 38, 38 in another direction of movement. Thebrackets 31, 31 are preferably made integral with the arms 38, 38 andare attached to the angle member 36 as by the bolts and nuts 46, 46.Rigidly attached to the angle member 36 is a rake or scraper plate 41provided with the lateral shoulders 48, 48 extending to each side of theangle member 36 and provided adjacent the bottom thereof with theprojecting teeth 49. As best illustrated in Fig. 4, said teeth 49 haveappreciable length and in normal operation are intended to projectcompletely through the screen bars l3 of the screen A. Said teeth 49,however, are shorter than the side plates l9, It! thus allowing for thelateral bars I2 to be attachedto the projections l2 on the screen barsl3 and to said side plates |0, I0 and yet provide clearance of saidteeth 49 when they are fully interleaved with the screen bars.

Also carried by the angle member 36 and rigidly attached thereto, as bywelding, is a. reinforcing weighting'bar 58, the principal function ofwhich is to add weight to said rake or scraper C to maintain the abovementioned interleaving relation when said rake or scraper is carryingrefuse during its upward movement.

The guide tracks B are preferably provided with the cam members 5| whichare adapted to lift the rake C, as it reaches its downward position,from the pins 45, 45 upon which the arms 38, 38 thereof normally restduring the downward travel of said rake or scraperC, to a positionadjacent the projecting stop lugs 44, 44. Said cams 5| rotate said rakeor scraper C by virtue of engagement of the lateral shoulders 48, 48with the upper portion of said cams 5|.

The cams 5| are terminated when the gravitational force on the rake orscraper C is effective to draw the arms 38, 38 against the stop lugs 44,44 rather than tending to move said arms 38, 38 towards the stop lugs45, 45. By virtue of this arrangement a shock, otherwise incident to therotation of the rake or scraper C about the axes 39, 39 as the arms 38,38 of said scraper C move from stops 45, 45 to stops 44, 44 incident tothe moving of the chains 2|, 2| around the lower bend of the guidetracks B, is effective prevented.

It' is to be particularly noted that due to the .horizontal extensionsl5 of the screen bars I 3,

l3, the interleaving of said bars and the teeth 49 of the rake orscraper C takes place at a position appreciably in advance of the area.on said screen A at which refuse or solid matter tends to accumulate.Theconcentrated area of accumulation will be adjacent the curved portionof said screen A designated by'the character G in Figs. 2, 3 and 5. Byvirtue of the above mentioned interleaving of said teeth 49 and thescreen bars |3 in advance of the area ofconcentration of refuse, it hasbeen discovered that prior tendencies for the teeth 49 to ride over thescreen A rake or scraper C thereacross. As illustrated by the dottedline representations of the rake or scraper C, in Fig. 3, the teeth 49thereof first begin to interleave with the extensions l5 at an upstreamposition well in advance of the area of-accumulation G, and slightlydownstream of the brackets I whereby the lake or scraper teeth clearsaid brackets l5 yet are fully interleaved with the extensions |5 beforereaching the accumulated refuse area. The position at which the firstinterleaving takes place is indicated by the dotted line representationof the rake or scraper C at the left of Fig. 3 and a full interleavedposition with the tips of teeth 49 riding on the plate I4 is illustratedin the second dotted line representation of said rake or scraper. Aposition of the rake or scraper C intermediate the positions indicatedby the dotted line representations of Fig. 3 is seen in Fig. 5 at whichposition the teeth tips are just coming into contact with the plate l4.The elongated construction of the teeth 49 whereby they projectrearwardly beyond the screen bars I3 is also effective to clean saidscreen A efficiently, for any refuse or foreign matter that may becaught between the screen bars I3 will be effectively drawnout by saidrake or scraper C which, as may be noted from Fig. 3, forms an obtuseangle with said screen bars l3.

It has been discovered, however, that sometimes due to a heavyaccumulation of refuse at the area G or to the accumulation of largepieces of fibrous material at said area, there may be a tendency for theteeth of said rake or Scraper C to be disengaged from their interleavingrelation with said screen bars l3. To prevent this disengagement exceptunder conditions of unusual load as, for example, when a large piece ofsolid matter like a rock or brick is found on said screen A, theleaf-spring cams 52, 52 are provided and carried on the lower anglemembers 20, 28

of the guide tracks B to maintain yieldingly the interleaving relationof saidteeth 49 and said screen bars l3. Said cams 52, 52 are adjustablyattached to the bottoms of the guide tracks B as by the brackets 53, 53.provided with the elongated slots 54 through which extend fasteningbolts provided with nuts. By loosening the nuts of said bolts, theposition of said bracket 53 may be adjusted and thereby adjust theposition of the cam 52 relative to said screen A. The forward end of thecam 52 is looped back on itself to form a U and provides a. bearingsurface 55 adapted to bear against the lower face of said lower anglemember 28 and to be freely movable with respect thereto.

In normal operation when the rake or scraper C is in proper interleavingrelation with the screen bars |3 of the screen A, the lateral shoulders48, 48 of said screen A do not come in contact with the lower surface ofsaid cams 52, 52. However, should the accumulated refuse at said area G,or at any area along said screen A opposite the earns 52, 52, tend todisengage said teeth 49 from said screen bars l3, said cams 52, 52 willbe effective to maintain yieldingly this interleaving relation. However,saidinterleaving relation is not positively maintained by said cams 52,52 and, should a large particle of material require the disengagementthereof to prevent damage to-the rake or scraper C, said cams 52,52'will yield and allow said disengagement.

The combination of the screen A with the horizontally-extendingprojections on the screen bars l3 and the cooperating leaf-spring cams52, 52 is very effective to provide and maintain a proper interleavingof the teeth 49 of the said rake or scraper C with the screen bars l3 ofthe screen A to remove effectively anyrefuse or solid matter accumulatedon said screen A-or lodged between the screen bars 13 thereof and yetprovide for the disengagement of said rake or scraper C from said screenA should said disengagement become necessary to prevent damage to therake or scraper, or to the screen A.

In the operation of my device, the driving mechanism is effective todrive the draft chains 2|, 2| in the guide tracks B, eithercontinuously, intermittently, as by the means disclosed in my abovementioned application, or at the will of an operator, as by manualcontrol. The chains 2 I, 2| and guide tracks B carry the rake or scraperC downwardly along the upper portion of the guide tracks B, with thearms 38, 38 of said rake or scraper C resting against stop lugs 45, 45.As the rake vor scraper C reaches cams 5|, 5| the shoulders 48, 48thereof ride upon the top sur-. face of said cams 5|, 5| and arms 38, 38are pivoted about pivots 39, 39 in their movement toward stop lugs 44,44. Cams 5|, 5| terminate when said rake or scraper C has reached aposition in which the force of gravity acting thereon is effective tomaintain arms 38, 38 adjacent said stop lugs 44, 44. Cams 5|, 5|, thusprevent any shock to chains 2|, 2| incident to the movement of rake orscraper C from a position where arms 38, 38 rest against stop lugs 45,45 to a position where they rest against stop lugs 44, 44.

As the rake or scraper C moves downwardly around the lower curvedsurface of the guide tracks B, the teeth 49 thereof interleave with theextensions |5 of the screen bars |3 forming screen A. This interleavingtakes place at a position wellv in advance of the area G on said screenat which the greater amount of solid matter tends to accumulate, thusproviding for the.

proper interleaving of the rake or scraper teeth before they are calledupon to do any work, and at a position where there is little possibilityof any accumulated refuse which might prevent said interleaving. Innormal operation the weight of the rake or scraper C is effective tomaintain the interleaved relation thereof with the screen bars of thescreen even when there is a large accumulation of refuse on said screenA, particularly at area G. However, if this accumulation is very heavy,or is of a particular kind of material,

such as fibrous material, it may tend to disen- I gage said teeth fromsaid screen bars. Leafspring cams 52, 52 are effective upon a slightlifting of the rake or scraper C from the screen A, to contact theshoulders 48, 48 of said rake or scraper to maintain yieldingly saidinterleaved relation, but are adapted to yield and allow actualdisengagement of the teeth from said screen bars should some extremecondition require such action to prevent damage to the rake or scraperor to any other part of the device.

As the rake or scraper C moves upwardly along the screen A, the teeth-49project entirely through the screen bars I3 of the screen A and thuspull out any material caught between adjacent bars, as well as removingany refuse accumulated on the surface of said screen.

As the rake or scraper C approaches the curved plate I8, it is tiltedabout its axes 39, 39 by the engagement of teeth 49 with a plate at thetop of said screen A whereby the teeth 49 disengage the screen bars l3and slide across the curved device, not shown, such as a traveling beltconveyo'r, receptacle or grinder, or on the floor If.

Incident to the discharge of said refuse, the

rake or scraper cleaner bar 88 wipes across the face of the rake orscraper and removes downwardly any refuse which tends to adhere thereto.sprocket wheels 24, 24 and again moved down the upper track of the guidetracks B.

While only one particular arrangement of the frame D, screen A and guidetracks B, has been illustrated and described in thisparticular'application to which my improved construction has beenapplied, it is obvious that the spring leaf cams may be applied to anyof the guide tracks disclosed in my above mentioned co-pendingapplication and that the extensions l5 of the screen bars may be appliedto any of the screens disclosed in saidv application.

While in the preferred form the horizontal extensions |5 of the screenbars [3 are formed by bending each screen bar adjacent the area G andthus forming each screen bar I3 from a single bar of material, saidextensions may be formed by the welding of the horizontal portionsthereof to the upwardly-inclined portions thereof adjacent the.area G.This latter construction may particularly be employed when the screen Ahas been previously constructed without the horizon tal extensions iiiof the screen bars l3.

In the construction of the device, the screen A is fabricated with theplate It and channel bar l1 welded thereto. In building the tank ortrough H and the floor I'I, excavations are provided to receive saidplate l4 and channel bar I1.

Threaded lugs H) are anchored integral withthe side walls of said troughor tank when it is constructed. The screen A is lowered vertically intoplace with the notches II registering with the lugs ID. The extensionsI5 project beyond the plate M- at I6 and at this point may rest on thebottom of the tank or trough adjacent an edge of the excavation which isbelow the piate M. This extension at l6 thus helps properly place thescreen while grout is poured into the excavation below plate M to fillit and anchor said plate I4 to the bottom of said tank or trough. Thefloor I'I being excavated to receive the channel I1 is also filled withgrout to anchor said channel, after the screen A is in place.

As this application is for an improvement of the material handlingapparatus disclosed in my co-pending application Serial No. 701,548filed December 8, 1933, the claims are, in general, restricted tofeatures not shown or described in said co-pending application. It is tobe distinctly understood, however, that the patentable subject matterdisclosed but not claimed in this application is not dedicated to thepublic but is claimed in said co-pending application. Purely asillustrative, and not as exhaustive, it may be stated the claims of saidco-pending application cover the general construction of the guidetracks herein disclosed, the general relation of said guide tracks tothe screen, the rake cleaning mechanism, the shock preventing camsmounted on the guide tracks, the combination of the screen with a floorplate, the particular discharge plate construction for the screen, thelateral spacing and supporting bars for the screen bars, the particularmounting of the rake on the conveyor chains, as well as numerous otherstructural details and combinations of elements not herein specificallyclaimed.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from the spirit. andscope of the invention as defined by' the claims hereto appended, and Iwish therefore not to be The rake or scraper'C is then carriedaroundnation with a screen having screen bars through which refusecarrying liquid is to be passed, a pivoted scraper provided with teethadapted to interleave with said bars as said scraper moves relatively tosaid screen, and stationary yieldable cam means to maintain yieldinglysaid interleaved relation.

2. In a liquid screening apparatus, the combination with a screenhavingupwardly-extending screen bars through which refuse carrying liquid isto be passed, spaced draft guides adjacent the edges of ,said screen onthe up-stream side thereof, draft means carried in said draft guides, atoothed scraper carried between said draft means, and cam means adaptedto maintain an interleaving relation between the teeth of said scraperandsaidscreen bars as said scraper moves upwardly along the face of saidscreen, said cam means comprising spring leaves attached to said draftguides.

3. In a liquid sceening apparatus, the combination with a screen havingupwardly-extending screen bars through which refuse carrying liquid isto be passed, spaced draft guides adjacent the edges of said screen onthe up-stream side thereof, draft means carried in said draft guides, atoothed scraper carried between said draft means, and cam means adaptedto maintain an interleaving relation between the teeth of said scraperand said screen bars as said scraper moves upwardly along the face ofsaid screen, said cam means comprising spring leaves attached at one endthereof to said draft guides.

4. In a liquid screening apparatus, the com-' bination with a screenhaving upwardly-extending screen bars through which refuse carryingliquid is to be passed, spaced draft guides adjacent the edges of saidscreen on the up-stream side thereof, draft-means carried in said draftguides, a toothed scraper carried between said draft means, and cammeansadapted to maintain an interleaving relation between the teeth of saidscraper and said screen bars as said scraper moves upwardly along theface of said screen, said cam means comprising spring leaves attached atone end thereof to said draft guides and loosely bearing against saidguides at their other ends.

5. In a liquid screening apparatus, the combination with a screen havingupwardly-extending screen bars through which refuse carrying liquid isto be passed, spaced draft guides adjacent the edges of said screen onthe up-stream-side thereof, draft means carried in said draft guides, atoothed scraper carried between said draft means, and cam means adaptedto maintain an interleaving relation between the teeth of said scraperand said screen bars as said scraper moves upwardly along the face ofsaid screen, said cam means comprisingcurved spring leaves adjustablyattached to said draft guides.

6-. In a liquid screening apparatus, the combination with a toothedscraper, of means for guiding said scraper, draft means for moving saidscraper, a screen having screen bars adapted to be interleaved with thescraper teeth, said bars having a non-screening substantially horizontalportion and a rectilinear inclined portion, means preventing-a flow ofliquid through said non-screening portion, said scraper being guided bysaid guide means to interleave said teeth with the horizontal portion ofsaid screen bars as said scraper is moved across said screen.

7. In a liquid screening apparatus, the combination with a toothedscraper, of means for guiding said scraper, draft means for moving saidscraper, a screen having screen bars forming a screening area andadapted to be interleaved with the scraper teeth, said screen barsextending beyond said screening area and approaching a horizontalnon-screening position, said scraper being guided by said guide meansto.

interleave said scraper teeth and screen bars adjacent the horizontalposition of said bars,

and stationary yieldable cam means adapted to maintain said interleavedrelation.

8. In a liquid screening apparatus, the combination with a screenthrough which refuse carrying liquid is to be passed, spaced scraperguides positioned adjacent said screen, a pivoted scraper carried bysaid guides and adapted to move over said screen to remove theaccumulated refuse,

and yielding cams carried by said guides adapted yieldingly to maintainsaid scraper in refuse removing relation with said screen.

9. A screen adapted to remove refuse from a refuse carrying fluidcomprising spaced screen bars each having an upwardly inclined screeningportion, a substantially horizontal non-screening portion constructedand arranged to form a guide for a rake, means constructed to prevent aflow of fluid through said non-screening portion, and a smooth concavecurved portion connecting the inclined portion and the horizontalportion and forming a refuse accumulating area.

10. In a liquid screening apparatus, the combination with a trough,,of ascreen adapted to remove refuse from liquid passing through said trough,a portion of 'said screen being rectilinearly inclined upwardly throughsaid, trough and another portion being parallel with the bottom of saidtrough and being attached to a plate parallel therewith, a rake adaptedto interleave with both portions of said screen, and means for movingsaid rake relative to said screen.

11. In a liquid screening apparatuathe combination with a screen, of arake adapted to be moved with respect, thereto, draft means for movingsaid rake, and cam means adapted to maintain said rake in operativerelation with said screen, said cam means being adjustably mounted atone end by a bracket having a pair of elongated slots, and boltsextending through said slots and into said guide means.

12. In a liquid screening apparatus, the comb nation with a screen, of arake adapted to be moved with respect thereto, draft means for saidrake, and cam means adapted to maintain said rake in operative relationwith said screen, said cam means being rigidly secured at one end andnon-rigidly secured at the other end, said nonrigidly secured end havingsliding contact with a surface. r v

13. In a liquid screening apparatus, the combination with a screenformed by rectilinear upwardly extending screen bars through whichrefuse carrying liquid is to be passed, of horizontal extensions onatleast some of said screen bars adjacent the bottoms thereof which forma concave upper surface forming a refuse accumulation area beyond whichsaid extensions project-upstream, a rake having teeth adapted tointerleave with said bars, guide means for said rake wherebysaidinterleaving begins with said extensions upstream of said refuseaccumulation area, said rake teeth having sufllcientlength to extendthrough said bars, and a plate positioned below said extensions forsufficient distance that the rake teethride on the top surface thereofuntil said refuse accumulation area is reached whereupon they projectthrough said screen.

14. In a liquid screening apparatus, the combination with a screenformed by rectilinear upwardly extending screen bars through whichrefuse carrying liquid is to be passed, of horizontal extensions on atleast some of said screen bars' adjacent the bottoms thereof which forma concave upper surface forming a refuse accumulation area beyondwhichsaid extensions project upstream, means preventing a flow of liquidbetween said horizontal extension, a rake having teeth adapted tointerleave with said bars, guide means for said rake whereby saidinterleaving begins with said extensions upstream of said refuseaccumulation area.

ROBERT E. BRIGGS.

